In modern computing there has recently been considerable attention paid to improving the user interface in an effort to create an operating environment that is easy and efficient to use. The term operating environment in this context refers to everything in a computer that a user can directly access and utilize in a unified and coordinated manner. In improving the user interface, there have been various efforts to create an operating environment that is integrated, that is, one which allows activities for various applications to be interweaved without losing an accumulated information and without sacrificing capability.
One aspect of integration focuses on the ability to access multiple applications or processes that reside in the computers main memory utilizing a single key stroke, command, or cursor movement within "windows". A window is a viewing area on a video display which may be a full screen region or smaller, and represents a bordered region, typically of rectangular shape, into which display data from application programs and the like are written. The use of a multiple window graphic interface is one approach in modern computing to creating a "desktop" metaphor interface.
In typical prior art video display systems and memory architectures, a single application program is implemented at one time. Thus, the application program can write directly to the video display buffer without interfering with concurrent display data output, because only display data of that single application program is displayed.
In recent attempts to create windowing environments, for computers using prior art memory structures, data, such as alphanumeric characters or graphic images to be displayed within single or multiple windows are temporarily stored in a video display buffer and then written directly to the video display. A particular application program running in the windowing environment must call the environment to determine the size and location and video display ownership priority of the current window.
In the prior art, display data from an application program is written only to that portion of the video display defined by the window which the program has identified. If a window on the video display is moved, or its size or ownership priority changed, the application program must be designed to implement a change in the display data that will be written to that window. Thus, to use existing application programs in prior art windowing environments, the program typically must be rewritten to accommodate for the architecture of that particular windowing environment. Thus, effective operation of the environment is "program dependant".
In addition, the video display buffer in prior art systems must be continuously updated since there is no high speed reference means for determining when there has been a change in display output data.
When an environment is introduced to the display system, such as a windowing environment, windows, (e.g. bounded or boardered regions), and display data, (e.g. application programs), typically appear on the video display concurrently. Also, display data from a particular application program typically must be written into a single window defined by the environment on the display, rather than to the entire display area. In the prior art, this accomplished by providing an operating environment that requires application programs to call the operating environment to determine current window parameters, and to insure that application program display data is written into selected windows. Thus, the prior art systems suffer the drawback of requiring that the application programs be structured or rewritten to call the operating environment instead of writing directly to the video display.